1. Field of the Invention
This invention relates to a process for preparing 1,2-amino alcohols.
2. Description of the Background Art
1,2-Amino alcohols (sometimes called beta-aminoalcohols) are compounds with an amino group and a hydroxyl group on adjacent carbon atoms. They are of considerable commercial importance, particularly in the pharmaceutical industry. Many 1,2-amino alcohols are important as drugs or as intermediates for the preparation of drugs (D. Lednicer and L. A. Mitscher, "The Organic Chemistry of Drug Synthesis", John Wiley and Sons, New York, 1977, pp. 62-84). Additionally, 1,2-amino alcohols are useful intermediates for the preparation of various heterocycles such as oxazolines (J. A. Frump, Chem. Rev., 71, 483 (1971)) or aziridines (I. Okado, K. Ichimura, R. Sudo, Bull. Chem. Soc. (Japan), 43, 1185 (1970)).
Of the several methods which have been developed for the preparation of 1,2-amino alcohols, few are general, versatile, provide high yields, or employ readily available starting materials.
A method for the synthesis of 1,2-amino alcohols which is similar to the process of the present invention has been reported in I. Elphimoff-Felkin, Bull. Soc. Chem. Fr., 784 (1955). In this method, the tetrahydropyranyl ether of a cyanohydrin, ##STR1## was reacted with a Grignard reagent, R'MgX, and then the intermediate product was reduced with lithium aluminum hydride (LiAlH.sub.4). One shortcoming of this method is the necessity of first converting a ketone to its cyanohydrin, then converting this cyanohydrin to its tetrahydropyranyl ether. Both steps occur with varying degrees of efficiency, and yields are not uniformly high. A second shortcoming is that the reaction was not demonstrated to be general, i.e. applicable with essentially any ketone, since the only examples reported were with acetone, cyclopentanone, and cyclohexanone. The third shortcoming is that the only reducing agent which was demonstrated to be effective for reduction of the intermediate product was lithium aluminum hydride, LiAlH.sub.4, and its use provided only poor to moderate yield of product. In addition, lithium aluminum hydride is a hazardous reagent.